Researchers and engineers have been advancing the research and development of a thin-film battery mainly as a battery having a capacity as extremely small as several to several tens of microampere-hours among all-solid-state batteries. The battery has a laminated structure in which, for example, a positive-electrode layer, a solid electrolytic layer, and a negative-electrode layer are placed successively either on a metal foil used as a collector or on a metal film formed on a ceramic substrate made of, for example, alumina. The individual layers are produced through the vapor deposition method, such as the sputtering method. The solid electrolytic layer is formed by using an oxide, and the negative-electrode layer is formed by using metallic lithium (see Patent literatures 1 and 2, for example).
On the other hand, there is another type of battery, which has a structure in which the positive-electrode layer and the negative-electrode layer are juxtaposed on the same plane, without laminating them (see Patent literature 3, for example). This battery has a positive-electrode layer provided on a positive-electrode-side collector formed on a substrate and a negative-electrode layer provided on a negative-electrode-side collector formed on the same substrate. Both collectors and both electrode layers are formed to have the shape of the teeth of a comb. The comb teeth of the positive-electrode layer and the comb teeth of the negative-electrode layer are placed to mesh with each other such that a tooth of one polarity is sandwiched between two teeth of the other polarity. A solid electrolyte is placed between the comb tooth of the positive-electrode layer and that of the negative-electrode layer.
Patent literature 1: the published Japanese patent application Tokukai 2005-251417
Patent literature 2: the published Japanese patent application Tokukaihei 10-83838
Patent literature 3: the published Japanese patent application Tokukai 2006-147210 (FIG. 1).